Dental or surgical compressed air handpiece and turbine for such a handpiece

ABSTRACT

Compressed air handpiece including a handle connected to a head housing a turbine. The turbine includes a moving wheel from a periphery of which extends a plurality of blades which define an outer diameter of the moving wheel. The handpiece also includes injection means, whose function is to direct onto the blades of the moving wheel a compressed air flow whose pneumatic energy is converted into kinetic energy when the compressed air flow strikes the blades of the moving wheel. The injection means take the form of an independent insert inside which is arranged a compressed air flow feed pipe and which is mounted inside the handle of the handpiece.

This application is a divisional of and claims the benefit of priorityunder 35 U.S.C. § 120 from U.S. patent application Ser. No. 14/533,726,filed Nov. 5, 2014, which is based upon and claims priority fromEuropean Patent Application No. 13196222.7, filed Dec. 9, 2013, theentire contents of both of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention concerns a dental or surgical compressed airhandpiece and a turbine for such a handpiece. The present inventionconcerns, in particular, a compressed air handpiece having increasedpower.

BACKGROUND OF THE INVENTION

The present invention concerns the field of handpieces for dental orsurgical use. There are two families of handpieces: contra-anglehandpieces which are equipped with an electrical motor and handpieceswhich include a turbine driven by compressed air.

We are concerned here with compressed air handpieces. In very simpleterms, these compressed air handpieces include a head which houses aturbine. This turbine includes a compressed air feed pipe and a movingwheel provided with a plurality of regularly spaced blades at theperiphery thereof. The feed pipe is used to force onto the turbineblades a compressed air flow whose pneumatic energy is converted intokinetic energy when the compressed air flow strikes the blades of themoving wheel.

FIG. 1 annexed to the present Patent Application is a perspective,cross-sectional view on a horizontal plane longitudinally intersectingthe handle and the head of a compressed air handpiece according to theprior art. Designated as a whole by the general reference numeral 1,this handpiece includes a handle 2 which is connected to a head 4 whichhouses a turbine 6. Turbine 6 includes a moving wheel 8 from a periphery10 of which extends a plurality of blades 12, which define an outerdiameter 14 of moving wheel 8.

Handpiece 1 also includes injection means whose function is to directonto blades 12 of moving wheel 8 a compressed air flow whose pneumaticenergy is converted into kinetic energy when the compressed air flowstrikes blades 12 of moving wheel 8. The compressed air injection meansare formed of a compressed air feed pipe 16 which is machined in handle2 of handpiece 1 using conventional techniques. Further, an airdischarge pipe 18 is also machined by conventional techniques in handle2 of handpiece 1, substantially parallel to and remote from compressedair feed pipe 16.

An examination of FIG. 1 reveals that compressed air feed pipe 16 isformed of a first and a second rectilinear pipe, respectively 20 and 22,arranged in the extension of each other, the longitudinal axis ofsymmetry 24 of second rectilinear pipe 22 extending slightly slantwiserelative to longitudinal axis of symmetry 26 of handle 2 of handpiece 1and making a non-zero angle α with the tangent 28 to outer diameter 14of moving wheel 8. It is clear that it is difficult to envisagemachining compressed air feed pipe 16 in a direction which would tend tomove closer to the tangent 28 to outer diameter 14 of moving wheel 8without risking piercing air discharge pipe 18 or having to reduce thediameter of pipe 18.

A recurrent problem facing designers of compressed air handpieces liesin the conversion efficiency between the pneumatic energy of thecompressed air and the kinetic energy of the moving turbine wheel.Indeed, the mechanical power that the compressed air handpiece candeliver depends on this conversion efficiency. This conversionefficiency is closely connected, in particular, to the drop in pressurebetween the pressure of the compressed air which penetrates the head ofthe handpiece, and the pressure of the air leaving the head of thehandpiece after the compressed air has struck the turbine blades.Indeed, the greater the pressure drop, the better the conversion betweenpneumatic energy and kinetic energy. The conversion efficiency betweenpneumatic energy and kinetic energy is also improved if the air flowoccurs with minimal turbulence and thus minimal losses. It is alsosought to reduce the operating noise of compressed air handpieces and toprevent, as far as possible, the compressed air intended to activate theturbine from escaping into the patient's mouth.

SUMMARY OF THE INVENTION

It is an object of the present invention to answer the aforementionedobjects in addition to others by providing in particular a timepieceproviding higher mechanical power.

The present invention therefore concerns a compressed air handpieceincluding a handle, which is connected to a head, which houses aturbine, the turbine including a moving wheel from a periphery of whichextend a plurality of blades which define an outer diameter of themoving wheel, the handpiece also including injection means, whosefunction is to direct onto the blades of the moving wheel a compressedair flow whose pneumatic energy is converted into kinetic energy whenthe compressed air flow strikes the blades of the moving wheel, thehandpiece further including a discharge pipe, arranged in the handpiecehandle and through which air is discharged after striking the blades ofthe moving wheel, the handpiece being characterized in that thedischarge pipe is at least facing the area in which the compressed airstrikes the blades of the moving wheel.

According to a complementary feature of the invention, the section ofthe discharge pipe extends over at least the height of the moving wheelblades.

According to another feature of the invention, the compressed airinjection means are arranged in the wall of the handpiece handle.

As a result of this feature, the present invention provides a compressedair handpiece in which the return of the compressed air, after it hasstruck the turbine blades, is greatly facilitated, which improves theconversion between the pneumatic energy of the compressed air and thekinetic energy of the turbine by facilitating the pressure drop betweenthe moment when the compressed air penetrates the head of the handpieceand the moment when the compressed air exits the head. It is understood,in fact, that whereas part of the compressed air goes around and drivesthe turbine, the other part of the compressed air ricochets onto theturbine blades and creates turbulence in the handpiece head. Thisturbulence considerably impedes the conversion efficiency betweenpneumatic energy and kinetic energy. By arranging the discharge pipe atleast facing the area in which the compressed air strikes the blades ofthe moving wheel, the present invention thus facilitates the evacuationof air which ricochets onto the turbine blades and thus makes itpossible to considerably reduce turbulence in the turbine head.

According to yet another feature of the invention, the compressed airinjection means take the form of an insert, inside which there isarranged a compressed air flow feed pipe, and which is placed inside thehandpiece handle.

According to yet another feature of the invention, the insert isarranged inside the discharge pipe.

According to yet another feature of the invention, the insert is mountedcoaxially inside the discharge pipe.

According to yet another feature of the invention, the insert isarranged so that the central axis of the compressed air flow extends ina tangential direction to the outer diameter of the moving wheel.

According to yet another feature of the invention, the compressed airflow feed pipe is formed of a first and a second rectilinear pipesarranged in the extension of each other, the second rectilinear pipehaving a longitudinal axis of symmetry which extends in a tangentialdirection to the outer diameter of the moving wheel.

As a result of these features, the present invention provides ahandpiece wherein the injection means take the form of an insertintended to be mounted inside the handpiece handle. The fact of using anindependent part makes it possible to channel the air flow in adirection tangent to the outer diameter of the moving wheel more easilythan in the case where the air feed pipe is machined by conventionaltechniques in the body of the handpiece. Indeed, in compressed airhandpieces, the turbine is arranged in a head which is typicallydisposed inside the extension of a generally rectilinear gripping handlepart inside which the compressed air feed pipe is machined. Unlesscomplex and therefore not economically viable measures are taken, it isnot possible to machine bent portions in the gripping handle part of thehandpiece using conventional techniques. Consequently, the compressedair feed pipe must be machined slantwise relative to the longitudinalaxis of symmetry of the handle part if the air flow is required tostrike the turbine blades in a direction which is close to the tangentto the outer diameter of the moving wheel. However, it must also bepossible to machine, in the handpiece handle, a discharge pipe throughwhich the air is discharged after striking the blades of the movingwheel. The inclination of the compressed air feed pipe relative to thelongitudinal axis of symmetry of the gripping handle part is thusnecessarily limited since, otherwise, the compressed air feed pipe wouldopen into the discharge pipe, which is technically unthinkable.

According to another advantage of the invention, the insert which servesto force the compressed air flow towards the blades of the moving wheelis mounted inside the discharge pipe arranged in the handpiece body andthrough which the air is discharged after striking the blades of themoving wheel. This arrangement facilitates the air return and thusgreatly promotes the pressure drop between the pressure of thecompressed air before it strikes the turbine blades and the pressure ofthe air exiting the handpiece head after striking the turbine blades.The higher the pressure drop, the better the conversion between thepneumatic energy of the compressed air and the kinetic energy of theturbine. This pressure drop is further amplified by the fact that theinsert is mounted coaxially inside the discharge pipe. The diameter ofthe discharge pipe can thus be increased, which makes it possible tobring the air pressure inside the handpiece head down to values close toatmospheric pressure. Finally, the conversion efficiency betweenpneumatic energy and kinetic energy is further improved because the airflow occurs with minimal turbulence and thus minimal losses. Further,the operating noise of the handpiece is reduced and virtually no air isdischarged into the patient's mouth.

According to another advantage of the invention, the injection meansforce the compressed air flow so that the compressed air flow strikesthe blades of the moving turbine wheel in a tangential direction to theouter diameter of the moving wheel. Consequently, this ensures thatmaximum torque is exerted by the air flow on the turbine blades, whichsubstantially increases the power provided by the turbine. By way ofexample, the power provided by current compressed air handpieces is onthe order of 13 watts, whereas the measured power of a compressed airhandpiece according to the invention is on the order of 20 watts.Therefore, with a compressed air handpiece according to the inventionpractitioners enjoy increased power, which allows them to work morequickly or to perform treatments which, until now, would have beendifficult to achieve using a compressed air handpiece due to theinsufficient power available.

The present invention also concerns a turbine for a compressed airhandpiece for dental or surgical use, said turbine including a movingwheel from the periphery of which extend a plurality of regularly spacedblades, the turbine being characterized in that each of the blades isformed of a first surface, which extends from the outer diameter of themoving wheel and which leads to a second surface, which extends along aradius of the moving wheel.

According to a preferred embodiment of the invention, the first surfaceextends from the outer diameter of the moving wheel to a point on theradius of the moving wheel from which the second surface extendsradially to the outer diameter of the moving wheel.

Finally, according to another feature of the invention, the blades areassociated in pairs in a stepped manner, each blade being separated fromits corresponding blade by a notch which extends in the direction of thecompressed air flow, so that the air flow is divided into two equalparts at the moment it reaches the notch. The object of this notch is toreduce the transit time from one blade to the next in order to limit themechanical power losses of the turbine.

The first surface leads the compressed air exiting the injection meanstowards the second surface. As the second surface extends along a radiusof the moving wheel and the compressed air flow is channeled in atangential direction to the outer diameter of the moving wheel, thecompressed air flow falls perpendicularly onto the second surface of theblade and then turns back. The mechanical power provided by a turbineincreases with the angle of deviation of the compressed air. In the caseof the present invention, the angle of deviation of the compressed airis 180°, which corresponds to optimum conversion between the pneumaticenergy of the compressed air and the kinetic energy of the turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will appear moreclearly from the following detailed description of one embodiment of acompressed air handpiece according to the invention, this example beinggiven merely by way of non-limiting illustration with reference to theannexed drawing, in which:

FIG. 1, already mentioned, is a perspective, cross-sectional view on ahorizontal plane longitudinally intersecting the handle and the head ofa compressed air handpiece according to the prior art.

FIG. 2 is a cross-section along a horizontal plane longitudinallyintersecting the handle and the head of a compressed air handpieceaccording to the invention.

FIG. 3 is a partially transparent side view of the head and the handleof the compressed air handpiece according to the invention.

FIG. 4 is a schematic diagram illustrating the first and second surfacesof a turbine blade.

FIG. 5 illustrates an improved variant embodiment of the turbineaccording to the invention.

FIG. 6 is a view of the back of the compressed air handpiece headaccording to the invention, in the area where the handpiece head isconnected to the handpiece handle.

FIG. 7 is a cross-section in a vertical plane passing through thelongitudinal axis of symmetry of the head and a portion of the handle ofthe compressed air handpiece according to the invention.

FIG. 8 is a schematic diagram of a variant embodiment of the compressedair handpiece according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

The present invention proceeds from the general inventive idea whichconsists in taking any measures necessary to increase the mechanicalpower that can be provided by a compressed air handpiece. To this end,the present invention attempts to optimise the conversion efficiencybetween the pneumatic energy of the compressed air and the kineticenergy of the moving turbine wheel. Indeed, the mechanical power thatthe compressed air handpiece can deliver depends on this conversionefficiency. This conversion efficiency is, in particular, closely linkedto the air flow conditions inside the turbine head. Indeed, it is knownthat, whereas part of the compressed air injected into the handpiecehead drives and goes around the turbine, another part of the compressedair simply ricochets onto the turbine blades and thus tends to turn backcreating turbulence in the handpiece head. By arranging the airdischarge means at least in the area into which this air is injected,the present invention facilitates the evacuation of compressed air whichricochets onto the turbine blades and which tends to create turbulencein the handpiece head. Conversion efficiency between the pneumaticenergy and kinetic energy is also linked to the angle at which thecompressed air strikes the turbine blades. This is why, according to afirst aspect, the present invention teaches creating the compressed airfeed means in the form of an insert placed inside the handpiece. Thefact of using an additional part enables the designer to enjoy muchgreater freedom as to the positioning of the insert than in the casewhere the designer should machine a compressed air feed pipe in thehandpiece handle using conventional techniques. According to anotheraspect of the invention, the compressed air feed insert is placedcoaxially inside the compressed air discharge pipe. This arrangementlimits turbulence and thus facilitates the air return, which promotesthe pressure drop between the compressed air pressure before it strikesthe turbine blades and the air pressure when it exits the handpiece headafter striking the turbine blades. The conversion efficiency between thepneumatic energy of the compressed air and the kinetic energy of themoving turbine wheel is thus also optimised. To achieve this result, thepresent invention also teaches channeling the compressed air flow in atangential direction to the outer diameter of the turbine of thecompressed air handpiece. Consequently, the compressed air flow strikesthe turbine blades perpendicularly to their surface, which ensures thatmaximum torque is exerted by the air flow on the turbine blades and thussubstantially increases the power provided by the turbine. Finally, theturbine blades are each formed of a first surface which extends from theouter diameter of the moving wheel and leads to a second surface whichextends along a radius of the moving wheel away from the centre of themoving wheel. The compressed air thus falls perpendicularly onto thesecond surface of the blade and is driven backwards with a deviation of180°. The greater the deviation angle of the compressed air flow, thegreater the force exerted on the turbine blades. Finally, the operatingnoise of the turbine according to the invention is limited and work isperformed almost at atmospheric pressure, so that very little air isdischarged into the patient's mouth.

FIG. 2 is a cross-section on a horizontal plane longitudinallyintersecting the handle and the head of the compressed air handpieceaccording to the invention. Designated as a whole by the generalreference numeral 30, the handpiece according to the invention includesa handle 32 which is connected to a head 34 which houses a turbine 36.Turbine 36 includes a moving wheel 38 from a periphery 40 of whichextends a plurality of blades 42, which define an outer diameter 44 ofmoving wheel 38.

Handpiece 30 also includes injection means whose function is to directonto blades 42 of moving wheel 38 a compressed air flow whose pneumaticenergy is converted into kinetic energy when the compressed air flowstrikes blades 42 of moving wheel 38.

To this end, the compressed air injection means take the form of anindependent insert 46 mounted inside handpiece 30 and inside which thereis arranged a compressed air flow feed pipe 48. In a preferred butnon-limiting manner, pipe 48 is arranged so that the central axis 50 ofthe compressed air flow extends in a tangential direction to the outerdiameter 44 of moving wheel 38. The present invention therefore providesa handpiece 30 wherein the injection means force the compressed air flowso that the compressed air flow strikes the blades 42 of moving wheel 38of turbine 36 in a tangential direction to the outer diameter 44 ofmoving wheel 38. Consequently, this ensures that maximum torque isexerted by the air flow on blades 42 of turbine 36, which substantiallyincreases the power provided by turbine 36.

According to a preferred but non-limiting embodiment of the invention,the compressed air flow feed pipe 48 is formed of a first and a secondrectilinear pipe, respectively 52 and 54, arranged in the extension ofeach other, the longitudinal axis of symmetry 56 of the secondrectilinear pipe 54 extending in a tangential direction to the outerdiameter 44 of moving wheel 38.

According to yet another feature of the invention, insert 46, whichserves to force the compressed air flow towards blades 42 of movingwheel 38, is mounted inside a discharge pipe 58 arranged in handle 32 ofhandpiece 30 and through which air is discharged after striking blades42 of moving wheel 38. In a preferred but non-limiting manner, insert 46is mounted coaxially inside discharge pipe 58.

The above arrangement greatly promotes the pressure drop between thecompressed air pressure before it strikes blades 42 of turbine 36 andthe pressure of the air exiting head 34 of handpiece 30 after strikingblades 42 of turbine 36. The higher the pressure drop, the better theconversion between the pneumatic energy of the compressed air and thekinetic energy of turbine 36. This pressure drop is further amplified bythe fact that insert 46 is mounted coaxially inside discharge pipe 58.The diameter of discharge pipe 58 can thus be increased, whichfacilitates the air return and makes it possible to bring the airpressure in head 34 of handpiece 30 down to values close to atmosphericpressure. Finally, the conversion efficiency between pneumatic energyand kinetic energy is further improved because the air flow occurs withminimal turbulence and thus minimal losses. Further, the operating noiseof the handpiece 30 is reduced and virtually no air leaks into thepatient's mouth occurs given that the pressure in head 34 of turbine 36is close to atmospheric pressure.

FIG. 3 is a partially transparent side view of head 34 and of handle 32of compressed air handpiece 30 according to the invention. As revealedby an examination of this Figure, each of blades 42 of turbine 36 isformed of a first surface 60 which extends from the outer diameter 44 ofmoving wheel 38 and which leads to a second surface 62 which extendsradially along a radius R of moving wheel 38.

More specifically (see also FIG. 4), the first surface 60 extends fromthe outer diameter 44 of moving wheel 38 to a point A on the radius R ofmoving wheel 38 from which the second surface 62 extends to the outerdiameter 44 of moving wheel 38. First surface 60 is advantageouslyplane, while second surface 62 has a profile in the shape of an arc of acircle tangential to the radius R of moving wheel 38. Preferably, firstsurface 60 forms a right angle with second surface 62.

Finally (see FIG. 5), according to a preferred variant embodiment of theinvention, blades 42 are associated in pairs in a stepped manner, eachblade 42 being separated from the blade associated therewith by a notch64 which extends in the direction of the compressed air flow F, so thatthe air flow F is divided into two equal parts F1 at the moment itreaches notch 64. The object of this notch 64 is to reduce the transittime from one blade to the next so as to limit mechanical power lossesin turbine 36.

From the foregoing it is clear that first surface 60 of blades 42 leadsthe compressed air exiting the injection means towards second surface62. Since second surface 62 extends along a radius R of moving wheel 38and the compressed air flow is channeled in a tangential direction tothe outer diameter 44 of moving wheel 38, the compressed air flow fallsperpendicularly onto second surface 62 of blade 42 and then turns back,deflected by the profile in the shape of an arc of a circle of secondsurface 62. The mechanical power provided by a turbine increases withthe angle of deviation of the compressed air. In the case of the presentinvention, the deviation angle of the compressed air is 180°, whichcorresponds to optimum conversion between the pneumatic energy of thecompressed air and the kinetic energy of turbine 36.

FIG. 6 is a rear view of head 34 of compressed air handpiece 30according to the invention, in the area where head 34 of handpiece 30 isconnected to handle 32 of handpiece 30; and FIG. 7 is a cross-sectionalview in a vertical plane passing through the longitudinal axis ofsymmetry of head 34 and of a portion of handle 32 of compressed airhandpiece 30 according to the invention. These two Figures clearly showthat insert 46, which serves to force the compressed air flow towardsblades 42 of moving wheel 48, is mounted inside discharge pipe 58arranged in handle 32 of handpiece 30 and through which air isdischarged after striking blades 42 of moving wheel 38. Preferably,insert 46 is mounted coaxially inside discharge pipe 58. Consequently,discharge pipe 58 is as large as possible and is as close as possible tothe compressed air flow feed pipe 58, which facilitates the air returnand maximises the pressure drop, so that the conversion between thepneumatic energy of the compressed air and the kinetic energy of turbine36 is optimised. An examination of FIG. 7 also reveals that the sectionS of discharge pipe 58 extends over at least the height H of blades 42of moving wheel 38.

According to yet another feature of the invention, insert 46 includesmeans of adjusting the position of the insert inside handle 32 ofhandpiece 30. According to an example given purely by way ofnon-limiting illustration, the adjustment means include an adjustingscrew 66 a foot 68 of which is received in a seat 70 arranged at theperiphery of insert 46. Seat 70 could be replaced by two flat portions.

It goes without saying that this invention is not limited to theembodiment that has just been described and that various simplemodifications and variants can be envisaged by those skilled in the artwithout departing from the scope of the invention as defined by theannexed claims. In particular, the present invention teaches that themeans of injecting compressed air preferably take the form of anindependent insert 46 mounted inside handpiece 30 and inside which isarranged a compressed air feed pipe 48. The object of this solution isto overcome the problems that those skilled in the art would encounterif they sought to machine slantwise a compressed air feed pipe usingconventional techniques in the, for example, stainless steel handle of ahandpiece. Another solution to the problem raised by the inventionexists however. Indeed, in the case where the handpiece is made bymoulding a material such as a ceramic, it may be possible to envisagedevising manufacturing moulds such that the feed pipe extends coaxiallyinside the discharge pipe. It is also possible to envisage making thehandpiece by the injection of a plastic material or a metallic material,this latter technique being better known as Metal Injection Molding orMIM.

According to a variant embodiment, the compressed air injection means 72are arranged in the wall 74 of handle 32 of handpiece 30 and thecompressed air discharge means 76 occupy most of the section of handle32. This type of arrangement can typically be obtained usingthree-dimensional printing techniques.

What is claimed is:
 1. A turbine for a compressed air handpiece fordental or surgical use, the turbine comprising: a moving wheel from aperiphery of which extend a plurality of blades defining an outerdiameter of the moving wheel and wherein the blades are configured to bestruck by a compressed air flow, wherein each of the blades includes afirst surface extending from the outer diameter of the moving wheel andwherein the first surface leads to a second surface extending along aradius of the moving wheel, wherein the first surface forms a rightangle with the second surface, the first surface leads compressed airejected from an insert towards the second surface, wherein thecompressed air flow falls perpendicularly onto the second surface,wherein the first surface extends from the outer diameter of the movingwheel to a point on the radius of the moving wheel from which the secondsurface extends radially to the outer diameter of the moving wheel,wherein the first surface is planar, and wherein the second surface iscurved with an axis of symmetry of the curved surface extendingperpendicular to an axis of rotation of the moving wheel such that thefirst surface is configured to lead the compressed air towards thesecond surface which is struck by the compressed air and then redirectsthe compressed air towards the first surface to provide an optimumconversion efficiency between pneumatic energy and kinetic energy, and amaximum torque.
 2. The turbine for the compressed air handpieceaccording to claim 1, wherein the first surface is planar.
 3. Theturbine for the compressed air handpiece according to claim 1, whereinthe plurality of blades includes at least two adjacent blades whereinthe second surface of one adjacent blade ends where the first surface ofthe other adjacent blade starts.
 4. The turbine for the compressed airhandpiece according to claim 1, wherein a number of blades is eight, andfor each blade, an angle formed by the second surface of the blade withthe first surface of an adjacent blade is 45°.
 5. The turbine for thecompressed air handpiece according to claim 1, wherein the curved secondsurface has a profile in a shape of an arc of a circle tangential to theradius of the moving wheel.
 6. The turbine for the compressed airhandpiece according to claim 1, wherein the turbine is connected to ahandle of the compressed air handpiece, the handle including an insertthat injects the compressed air flow onto the plurality of blades, andfurther including a discharge pipe that discharges air after strikingthe plurality of blades, and wherein the insert and discharge pipe arecoaxially disposed.
 7. A turbine for a compressed air handpiece fordental or surgical use, the turbine comprising: a moving wheel from aperiphery of which extend a plurality of blades defining an outerdiameter of the moving wheel and wherein the blades are configured to bestruck by a compressed air flow, wherein each of the blades includes afirst surface extending from the outer diameter of the moving wheel andthe first surface leads to a second surface extending along a radius ofthe moving wheel, wherein the first surface is planar, wherein thesecond surface has a profile in a shape of an arc of a circle tangentialto the radius of the moving wheel, an axis of symmetry of the arc of thecircle being a horizontal axis perpendicular to an axis of rotation ofthe moving wheel, wherein the first surface extends from the outerdiameter of the moving wheel to a point on the radius of the movingwheel from which the second surface extends radially to the outerdiameter of the moving wheel, wherein the first surface is planar, andwherein the second surface is curved with an axis of symmetry of thecurved surface extending perpendicular to an axis of rotation of themoving wheel such that the first surface is configured to lead thecompressed air towards the second surface which is struck by thecompressed air and then redirects the compressed air towards the firstsurface to provide an optimum conversion efficiency between pneumaticenergy and kinetic energy, and a maximum torque.
 8. A turbine for acompressed air handpiece for dental or surgical use, the turbinecomprising: a moving wheel from a periphery of which extend a pluralityof blades defining an outer diameter of the moving wheel and wherein theblades are configured to be struck by a compressed air flow, whereineach of the blades includes a first surface extending from the outerdiameter of the moving wheel and wherein the first surface leads to asecond surface extending along a radius of the moving wheel, the firstsurface forming a right angle with the second surface and leadingcompressed air ejected from an insert towards the second surface, andthe compressed air flow falling perpendicularly onto the second surface,wherein the blades are associated in pairs in a stepped manner, whereinthe compressed air flow is divided into two equal parts at a moment whenthe compressed air flow reaches a notch based on each blade beingseparated from a blade associated therewith by the notch extending in adirection of the compressed air flow, and the notch reducing a transittime of the compressed air flow from one blade to another, wherein thefirst surface extends from the outer diameter of the moving wheel to apoint on the radius of the moving wheel from which the second surfaceextends radially to the outer diameter of the moving wheel, wherein thefirst surface is planar, and wherein the second surface is curved withan axis of symmetry of the curved surface extending perpendicular to anaxis of rotation of the moving wheel such that the first surface isconfigured to lead the compressed air towards the second surface whichis struck by the compressed air and then redirects the compressed airtowards the first surface to provide an optimum conversion efficiencybetween pneumatic energy and kinetic energy, and a maximum torque.